Reconstruction of paleoproductivity and paleotemperature recorded in sediment cores of Drake Passage and Scotia Sea, Antarctica

To reconstruct paleoproductivity related to paleoclimate change of the Southern Ocean, biogeochemical indicators, such as organic carbon and total nitrogen contents, and their stable isotopes ratios (δ13C, δ15N), biogenic opal, and biogenic barium contents, were determined using the sediment core GC98-06 (core length 251cm, in Drake Passage) and GC03-PW02 (core length 784cm, in Scotia Sea). And they were analysed GDGTs using high performance liquid chromatography-mass spectrometry (HPLC-MS) with an Agilent 1100 HPLC system connected to a Bruker Daltonics microTOF-HS time-of-flight mass spectrometer. The GC98-06 and GC03-PW02 cores have three interglacial periods (MIS1, MIS3, MIS5) and three glacial periods (MIS2, MIS4, MIS6). The average of C/N ratio (9.34 and 7.65, respectively) and δ13C values (-24.4‰ and - 24.6‰, respectively) in GC03-PW02 (Scotia Sea) and GC98-06 (Drake Passage) indicated that the organic matter in the sediment originated from marine primary production by phytoplankton. The BIT index as an indication of fluvial terrestrial input, is 0.03 (GC03-PW02) and 0.06 (GC98-06), suggesting little contribution of terrestrial organic matter. TOC, TN, Biogenic Opal and Biogenic Barium contents in the glacial periods (i.e., MIS 2, MIS 4, MIS 6 stage) are lower than in the interglacial periods. These results reflect that marine productivity increased during the interglacial periods. The average of TEX86-derived temperatures was lowest (0.5°C) in MIS1 periods and the highest (3.8°C) in MIS4 period of Drake Passage, and also the lowest (2.7°C) in MIS1 periods of Scotia sea. These TEX86-based temperature demonstrate that MIS1 period is unexpectedly the coldest in both sites.